Is this mystery find garden foe or friend?

Garden Detective: A cluster of little round “balls” suddenly appeared on a rock next to a Wilton pond. Most likely, those are moth eggs, says UC master gardener Rachel Tooker. Claudia Delezenski

Garden Detective: A cluster of little round “balls” suddenly appeared on a rock next to a Wilton pond. Most likely, those are moth eggs, says UC master gardener Rachel Tooker. Claudia Delezenski

Experts tackle readers’ garden questions.

Q: I’m wondering if you can identify what is on several rocks in our frontyard in Wilton. They appear to be maybe tiny eggs of some sort; some are very clustered and others are spread out. But then when I crushed a few, it seemed to be nothing but dust. So, I guess it could be some kind of spore.

Claudia Delezenski, Wilton

Sacramento County Master Gardener Rachel Tooker: Based on the massing and location of the tiny objects on the rock, as well as the color and apparent surface texture, these may be moth eggs. However, without more information, it is difficult to provide a definitive answer.

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If they are indeed some type of insect egg, recognizing the life stages will help determine if the bugs that emerge from the eggs are anything to be concerned about. Regular monitoring around the rocks and in the yard is key.

Every insect begins life as an egg, which hatches into an immature form called a nymph or larva. The insect then grows by periodically forming a new outer skin or exoskeleton (molting) and shedding the old skin. In addition to changing size, insects can modify their shape with each successive molt in a process known as metamorphosis. Insects that completely change form (complete metamorphosis) – such as caterpillars, moths and beetles – go from egg, to larva, to pupa and then to adult.

Typically, insects lay eggs close to a source of food for the growing larvae or nymphs to feed on. Eggs can be found under leaves, clustered on stems, in leaf litter under trees, along the edge of ponds or other standing water, and even on rocks. These eggs may have been laid on the rock for the emerging insect to eat rock lichen or a tasty nearby plant. If that is the case, an abundance of caterpillars may be soon found rapidly defoliating, tunneling into or skeletonizing an adjacent plant.

Because many insects tend to be host-specific in their eating preferences, damage to nearby plants will make it possible to link the eggs to the type of insect. Collecting samples of the insect, tracking how many there are in the yard and identifying the host plant will give important clues to whether the bug is a pest or a beneficial insect, and, if a pest, what steps to take, if any, to manage it.

Keep in mind that not all insects are bad. Of the 92,000 species that have been identified in the United States, about 87,000 (95 percent) are either good or neutral. In many cases, as long as good management practices are followed to keep plants healthy, they can withstand some insect feeding activity.

For information on identifying and managing pests in the home garden, visit the University of California Integrated Pest Management website at ipm.ucanr.edu.